In an electronic device such as a cellular phone, a PDA, or a notebook computer, a display unit is coupled to an operation unit in a foldable manner via a hinged portion, or a display unit is coupled to a vertically-oriented operation unit so that the display unit is slidable relative to the operation unit along a longitudinal direction in a state in which the display unit is overlaid on the operation unit. In most cases, the display unit has a vertically-oriented shape or a horizontally-oriented shape. Therefore, if the display unit is fixed in position, the usability is problematically impaired for a variety of different uses.
Japanese laid-open patent publication No. 2006-019925 has proposed a personal digital assistant having a rotation coupling mechanism for coupling a display unit to a vertically-oriented operation unit so that the display unit is slidable and rotatable relative to the operation unit. The rotation coupling mechanism is configured to use a rotational operation to change between a close state in which the display unit covers an operation part of the operation unit and an open state in which the operation part of the operation unit is exposed.
Furthermore, Japanese laid-open patent publication No. 2004-215180 has proposed a portable wireless terminal device in which a vertically-oriented operation unit and a vertically-oriented display unit are coupled to each other in a foldable manner by a coupling mechanism including a hinged portion and a slide rotation portion. The portable wireless terminal device is usually used along with an open/close operation using the hinged portion. The display unit is rotated through 90 degrees by the slide rotation portion as needed. Thus, the display unit can be changed between a vertically-oriented posture and a horizontally-oriented posture.